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The United States Supreme Court Invalidates Personalized Medicine Claims

March 21, 2012

The Supreme Court of the United States has dealt another blow to the Biotechnology Industry in its March 20, 2012, decision of Prometheus v. Mayo. Prometheus is the exclusive licensee of two United States Patents: 6,355,623 and 6,680,302, directed to methods of optimizing efficacy and safety of thiopurine drugs for treating autoimmune diseases. In a unanimous decision, Justice Breyer, speaking for the Court, invalidated the claims on the basis that they amounted to nothing more than claims to laws of nature, and upholding such a patent would “risk disproportionately tying up the use of the underlying natural laws, inhibiting their use in the making of further discoveries.” The impact of this decision remains to be seen but causes concern for the future of patenting in the field of personalized medicine.

By way of background, prior to the Prometheus patents, it was known that thiopurines could be used to treat immune-mediated gastrointestinal disorders. It was also known that levels of certain metabolites, such as 6-thioguanine, were correlated with the likelihood that a particular dosage could cause harm or prove ineffective. The inventors of the Prometheus patents determined that specific levels of the metabolites were correlated with the efficacy of the thiopurines. The Supreme Court was tasked with determining whether the claims at issue contained patent-eligible subject matter.

Claim 1 of the ‘623 Patent was considered by the Court as typical of all of the claims:


A method of optimizing therapeutic efficacy for treatment of an immune-mediated gastrointestinal disorder, comprising

(a) administering a drug providing 6-thioguanine to a subject having said immune-mediated gastrointestinal disorder; and

(b) determining the level of 6-thioguanine in said subject having said immune-mediated gastrointestinal disorder,

wherein the level of 6-thioguanine less than about 230 pmol per 8x108 red blood cells indicates a need to increase the amount of said drug subsequently administered to said subject; and

wherein the level of 6-thioguanine greater than about 400 pmol per 8x108 red blood cells indicates a need to decrease the amount of said drug subsequently administered to said subject.

The Court held that the claims are directed to laws of nature “namely, relationships between concentrations of certain metabolites in the blood and the likelihood that a dosage of a thiopurine drug will prove ineffective or cause harm.” The Court summarized several cases relating to the prohibition against the patenting of laws of nature and noted that certain prior cases held that an application of a law of nature may well be patentable. The Court then posed the question “do the patent claims add enough to their statements of the correlations to allow the processes they describe to qualify as patent-eligible processes that apply natural laws?”

In analyzing the steps of the claim, the Court held that none of the steps amounted to application of a law of nature. In fact, the Court referred to the “administering” step as simply referring “to the relevant audience, namely doctors who treat patients with certain diseases with thiopurine drugs.” With respect to the “determining” step, the Court held that the step “tells the doctor to determine the level of the relevant metabolites in the blood, through whatever process the doctor or laboratory wishes to use.” As expected, the Court held that third step, the “wherein” clause, simply tells the doctor about the laws of nature “at most adding a suggestion that he should take those laws into account when treating his patient.”

The Court then looked at the process as a whole and considered whether the three steps as an ordered combination added anything to the laws of nature and again the Court disagreed with Prometheus stating that “the claims inform a relevant audience about certain laws of nature; any additional steps consist of well-understood, routine, conventional activity already engaged in by the scientific community; and those steps, when viewed as a whole, add nothing significant beyond the sum of their parts taken separately.”

Justice Breyer summed up his analysis by saying “Other cases offer further support for the view that simply appending conventional steps, specified at a high level of generality, to laws of nature, natural phenomena, and abstract ideas, cannot make those laws, phenomena and ideas patentable.” He went on to say that they did not need to comment on what the result would be if the steps at issue were “less-conventional.”

The extent of the impact of this case is not yet known but many commentators are pessimistic. We are hopeful that the lower courts will interpret the decision as being limited in scope to these particular facts. There is some room to distinguish future cases by providing “enough” to move the claim from a law of nature to an “application” of a law of nature. Unfortunately, the Courts do not provide much guidance on what exactly would be sufficient to cross this judicially-created line. The Court does note that the steps in this case are “conventional” steps that are specified at a high level of generality. Thus, going forward, any non-conventional steps with particulars should be included in future claim drafting strategies.

Patentees concerned with the impact of this decision on their patents or pending patent applications are encouraged to contact us for further advice.

Melanie Szweras, B.Sc., Ph.D. (Genetics), LL.B., is a partner in Bereskin & Parr LLP's Biotechnology & Pharmaceutical practice group. She can be reached in Toronto at 416.957.1678 or

Micheline Gravelle, B.Sc., M.Sc. (Immunology), is a partner and the leader of Bereskin & Parr LLP's Biotechnology & Pharmaceutical practice group. She can be reached in Toronto at 416.957.1682 or

Content shared on Bereskin & Parr’s website is for information purposes only. It should not be taken as legal or professional advice. To obtain such advice, please contact a Bereskin & Parr LLP professional. We will be pleased to help you.


Melanie Szweras Melanie Szweras
B.Sc., Ph.D. (Genetics), LL.B.
416.957.1678  email Melanie Szweras
Micheline Gravelle Micheline Gravelle
B.Sc., M.Sc. (Immunology)
416.957.1682  email Micheline Gravelle